Perkins, who was placed on the 15-day disabled list Monday with left elbow inflammation, returned to Minnesota on Tuesday to have an MRI, which showed irritation of his ulnar nerve with mild swelling.
Fortunately for the southpaw, no structural damage was found. Twins manager Ron Gardenhire said Perkins will simply rest and wait to be re-evaluated before his stint on the DL ends.
Perkins' spot in the rotation will be filled temporarily by Anthony Swarzak, a right-hander called up from Triple-A Rochester after Craig Breslow was waived Wednesday.
Gardenhire said it is unclear what role awaits Swarzak after Perkins returns from the DL.
"We're just going to have him start and try to get through those starts," Gardenhire said. "If there's arguments and it looks like he might be able to help us out of the bullpen, then we'll make the arguments.
"We'd really like to keep this guy here even if it is out of the bullpen. But he's not done that [before]. And to ask him, one of our top young starting pitching prospects to go to the pen, we'd have to weigh this decision whether it was the right thing for him and the organization."
David Just is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.